PFAS in a private well in Sweden – PFAS4, PFAS21, test results and retesting
A practical guide to Swedish PFAS4 and PFAS21 drinking-water guidelines, private wells, laboratory samples and remediation records.
Short answer: From 1 January 2026 Sweden applies drinking-water limits of 4.0 ng/L for PFAS4 and 100 ng/L for PFAS21 at the specified points in regulated supplies. For a small private household well the corresponding levels are generally advisory Swedish Food Agency values, not legally binding limits. Evaluate the actual lab report, sample location and whether the water is for private or commercial use. PFAS cannot be detected by taste or colour.
Private household or regulated business?
The owner of a private well is responsible for testing and maintaining water quality. A well serving a café, rented accommodation, school or other public/commercial activity may instead fall under LIVSFS 2022:12. Some small regulated enterprises have tailored obligations and exceptions. Identify the legal category before stating that a threshold is legally binding.
What PFAS4 and PFAS21 actually measure
PFAS4 is the sum of PFOS, PFOA, PFNA and PFHxS. PFAS21 is a distinct wider sum of 21 listed substances. Testing only PFAS4 does not establish PFAS21. Ask the lab which analytes, reporting limits, calculation rules and units were used. Never automatically treat a below-quantification result as zero.
Decision table for your water report
| Sample situation | What needs to be checked |
|---|---|
| Private well, PFAS4 below 4.0 and PFAS21 below 100 ng/L | Both readings are below those PFAS advisory values; this does not establish that all other drinking-water quality parameters are satisfactory. |
| Private well with PFAS4 above 4.0 ng/L | Record the evidence and seek expert interpretation, local source information and advice on alternative drinking water or retesting. |
| Business water supply tested at the consumer tap | Review binding LIVSFS 2022:12 duties, the operator's programme and the correct water sampling point. |
| Raw water sample before treatment | Useful for assessing risk, but not itself the same as a regulatory exceedance in water at the user's tap. |
| Lab reports PFAS4 0.005 µg/L | This corresponds to 5 ng/L because 1 µg/L equals 1,000 ng/L. Confirm the parameter is indeed the PFAS4 sum. |
| One or more analytes are <LOQ | Reporting limits and lab summing rules require interpretation. Do not invent a precise numerical result. |
Seven steps after a concerning result
- Determine if the well serves only private use or also a commercial/public activity. Record the owner and number of users.
- Ask the local municipality about known PFAS sources such as former fire-training or industrial sites. An ordinary test may not include PFAS.
- Order an appropriate PFAS analysis from a laboratory accredited for the measurement and follow its sampling and container instructions.
- Record whether water was sampled untreated, after a filter or at the tap where it is consumed. Keep lab sample ID and date.
- Record the original PFAS4/PFAS21 sums, units, individual substances and reporting limits. Ask the lab to interpret uncertain values.
- Where findings cause concern, seek appropriate professional advice on alternative water, source investigation, retesting and potential treatment.
- Log the actions and costs. After installing any treatment, follow a qualified maintenance and post-treatment sampling plan.
Two laboratory-report examples
Case 1 – unit trap: A PFAS4 report of 0.0045 µg/L is 4.5 ng/L. Keep original and converted units visibly separate.
Case 2 – wrong sampling point: Untreated well water measures PFAS4 at 6 ng/L before filtration, but no tap water has been tested. Investigate the risk, but do not certify tap-water quality or filter performance from this sample alone.
What to do with elevated PFAS
Long-term intake of elevated PFAS may affect health, but a single lab result is not an individual diagnosis. The Swedish Food Agency advises investigating and addressing water above the guideline. The municipality can help identify local contamination; laboratories can clarify measurement uncertainty. Activated carbon and reverse osmosis may be treatment options but require correct selection, maintenance and testing. Boiling is not a way to remove PFAS. No filter is automatically certified by this guide.
Common questions about private wells
Is PFAS included in a standard private well test?
Not necessarily. A separate PFAS analysis is often appropriate when local contamination is plausible.
How often should a private well be tested?
The Swedish Food Agency advises at least every three years, or generally annually with children aged five or under or more than two households; suspected pollution may justify extra tests.
Can PFAS21 be calculated from PFAS4 alone?
No. PFAS21 comprises more specified substances; check what the lab actually measured.
Can a spreadsheet certify the water as safe?
No. A calculation or record cannot replace a complete lab analysis or qualified assessment.
Official sources and limitations
own · interpret · targets · regs · param · sampling · sgu
Sources reviewed 13 November 2026. General Swedish regulatory guidance for well owners, not individual medical advice, laboratory testing, an official water-quality certificate or a guarantee of filtration efficacy.
Related document templates
Get the editable Word, PDF and Excel package: PFAS in your own well 2026 – interpret PFAS4/PFAS21, request retesting and document actions | Word/PDF/Excel. Check the product description for its precise contents.
